srilanka ancient irrigation proposal

8/14/2019 SriLanka Ancient Irrigation Proposal

1/15

Format for Proposals of Candidate Systems

For The Globally-important Ingenious Agricultural Heritage Systems (GIAHS)

Programme

SUMMARY INFORMATION

a. Country and location

Sri Lanka

North Central Province

b. Project title / name of the system

Protection and revival of Ancient Irrigation Systems in Sri Lanka

c. Requesting agency

Central Engineering Consultancy Bureau

d. Governmental counterparts and other partners

Irrigation Department

Department of Agriculture, Rice research InstituteUniversity of Peradeniya

United Nations University

State Development and Construction Corporation

Institute for Fundamental Studies

e. Summary of objectives and activities (max. 200 words)

The ancient irrigation systems of Sri Lanka consist of intricate networks of small to

gigantic reservoirs called tanks connected through a series of feeder canals that

brought water for yearlong rice cultivation in the dry zone. The majority of tanks

that numbers around 30,000 have been constructed from 3rdcentury BC to 12th

century AD and some of them have been in operation continuously for more than

2000 years. The project aims to recognize and promote the multiple servicesprovided by these sustainable systems in agriculture, ecology and social sectors.

Through the development of a series of demonstration pilot system it aims to

revive the systems in the context of present day needs as an ecologically sound

development alternative. The specific activities are;

Document the technology and practices related to environmental, social and

economic perspectives of ancient irrigation systems

Choosing demonstration sites as pilot systems to highlight the multiple values

of irrigation tank systems through multi-stake holder consultation process

Develop a framework for reviving the tank based village system as a modern

day residential unit though the partnership of local communities, NGO,

government and educational institutes by exploring benefits in food security,

poverty reduction, bio-diversity and eco-tourism.

Develop a framework for systematic research and dissemination of sustainable

practices and experiences or the water heritage of Sri Lanka achieved

through the perfection of ancient irrigation systems.

DESCRIPTION OF THE SYSTEM

1. Description of GIAHS

The rainfall of the low dry lands, the most significant climatic zone for the rice production of Sri

Lanka, is concentrated in a rainy season of 3 months. Intricate irrigation systems consisting of


2/15

large number of interconnected reservoirs (wevaor tanks) evolved in response to this

climatology, during the period from 3 century B.C. to 12 century A.D. The ancient irrigation

systems in Sri Lanka still function as a crucial element in agricultural water supply in the dry

zone. These systems also constitute one of the richest sources of wetland biodiversity in the

country.

One of the intriguing features of the tank systems is their sheer density: There are about 30,000tanks which have been built in the land area of about 40,000 sq.km of the dry zone, resulting in

nearly a tank for every square kilometer (Mendis, 2003). This large density of tanks and their

long-term existence (more than 1000 years in many cases) make them an important component

in the environment and ecosystems of the region. Figure 1 shows the distribution of ancient tanks

in the North Central region of Sri Lanka.

Brohier (1934) identified that there is a chain like structure in organization of small tanks in Sri

Lanka and their relationship with large ancient reservoirs and waterways (Brohier, 1937) .

Madduma Bandara (1994) coined the term cascadesto identify this pattern where water from

upstream tanks was successively stored in those of downstream (figure 2). These small cascades

are linked to large reservoirs and giant feeder canals to form extremely complex large irrigationsystems (figure 3).

The technical breakthrough that enabled the construction of large irrigation systems in Sri Lanka

is the invention of the valve tower or the valve-pit. Sir Henry Parker, a British Engineer with

the irrigation department who was entrusted with rehabilitation of ancient irrigation systems in

mid 1800 describe the skills and inventions that went to the development of ancient tanks as

follows.It may be assumed, that the formation of all reservoirs of a class with embankments

much higher than those of simple village tasks was originally due to the constructive genius of

the Sinhalese themselves. . Since about the middle of last century, open wells, called valve-

towers when they stand clear of the embankment and valve-pits when they are in it, have been

built at numerous reservoirs in Europe. Their duty is to hold the valves, and the lifting gear forworking them, by means of which the outward flow of the water is regulated or totally stopped.

Such also was the function of the bisokotuwaof the Sinhalese engineers; they were the first

inventors of the valve-pit, more than 2100 years ago.(Parker, 1909)

Figures 4 and 5 show the short valve pit or short-sluice used to control the outflow of small

tanks. This construction made it possible to use a single sluice gate to distribute water to paddy

fields at any reservoir water level. However, it cannot accommodate high volumes associated

with large reservoirs. The bisokotuwa has been developed for this purpose (Avsadahamy,

2003). The figures 6-8 shows the details of bisokotuwa used in large reservoirs. Sir Henry

Parker (1909) describes the still intact bisokotuwa of Pawatikulam tank which had performed

its duties continuously for over 2100 years.

A tank system in a cascade has a small reservation catchment, the reservoir, a strip of trees

downstream of the reservoir that act as a wind breaking barrier, paddy fields, and the village. The

reservation of the next tank of the cascade starts immediately below the paddy fields of the upper

tank. The system of tanks, paddy fields and canals are so much integrated and inter woven with

the natural environment, it is difficult to identify tank systems as man made structures. The

primary service provided by the tanks was the storage of rainfall that comes in 3 months to

enable year long rice growing with two seasonal crops. In addition to irrigation water, the tanks

provided a number of other services. They made the microclimate pleasant and cool, enabled bio

and agro diversity. The tanks also served as the common bathing place for the village and the

meeting point for the village. (Photos 1 5). Most importantly the independence provided theancient tanks through to each village has paved the way for a unique decentralized social system

in Sri Lanka, where farmers had the highest social rank.


3/15

2. Goods and Services Provided by the System

About 40% of annual rice production in Sri Lanka originates from the dry-zone, where majority

of farmlands depend on the ancient irrigation systems for a sustained water supply. There are

two rice cultivation seasons,yala, October-March and maha, April-September. The mahalandpreparation and planting is generally started with the arrival of North-West monsoon rains, but

needs irrigation for managing the crops until harvesting during February-March. During the yala

season, the heavy rains of southwestern monsoon are limited to the south-western plans and

central mountains (collectively known as wet-zone). Therefore the possibility of farming a

second season almost entirely depends on irrigation.

In addition to the ancient irrigation systems, several large-scale irrigation projects (e.g.Mahaveli

Development Project during 70s and 80s) involving diversions and big dams contribute to the

irrigation water in the dry-zone in Sri Lanka However, these schemes also are designed to

depend on and to supplement to the function of some of the major components of the ancient

systems.

The development of tank irrigation system was a crucial element in the social organization and

cultural traditions in the dry-zone. Numerous villages in dry zone are having names synonymous

with the name of the village tank. The highly distributed nature of this water resource and the

sheer number density had no doubt contributed to the shaping of the social structures of people

that built, managed and reaped benefits of them. The nature of the system encourages a much

decentralized mode of water governance at the same time emphasizing the importance of inter-

relationships and co-operation at larger scales.

Sri Lankas low land also features a number of very large historical reservoirs that are believed

to be the products of a centralized state bureaucracy. When the states that supported themcollapsed (after 13thcentury), these works were also ruined. However, the village tanks (the

subject of this proposal) did not undergo the same destiny, because they were constructed,

managed and maintained by the respective villagers. It is believed that there had been a

sophisticated system of shared responsibility and social equity developed around the village tank

system (Traces of which still remains in remote parts of Sri Lanka). Until the colonial

government instated irrigation department in 1860s in fact, the management of village tanks

completely remained on the hands of the locals.

Sri Lankas ancient history provides several examples of cases where the states authority was

effectively challenged and sometimes overrun by the common opinion. In addition to cultural

and religious factors, historians increasingly see a contribution from the very decentralized and

independent nature of the village tanks systems towards the freedom of thinking. In fact, in the

ancient history of Sri Lanka (particularly the early period of the 2ndmillennium) there are

occasions showing a competition between the independent, self-sufficient villages and the desire

of central authorities to consolidate them in to state. One example is the King Parakramabahu the

great who reigned in Pollonaruwa from 1164 to 1197. The king was responsible for the

construction of a number of monumental tanks among which the famousparakrama samudra

takes a prime place.

Study of the history of Sri Lanka does not reveal evidence that a centralized bureaucracy ever

even existed to run the country's irrigation works (Leach, 1959). The necessary maintenance

work was organized by the villagers themselves: there was never a centralized bureaucracy to

direct such work or to ensure that it was carried out. (Goldsmith and Hildyard, 1984).

It is reasonable to assume that the social system organized around the village tanks in ancient Sri


4/15

Lanka was significantly different from the feudalism in the medieval Europe and many others

elsewhere in the world. Understanding this unique and sustainable way of life is also as

important as the scientific, economical and ecological aspects of the ancient tanks systems.

3. Threats and Challenges

It is widely accepted that the ancient irrigation system in the dry-zone of Sri Lanka was largely

developed during the period up to 12thcentury. The system faced a decline from 13 thcentury to

19thcentury (Panabokke, 1999) due to numerous reasons including poor soil conditions, malaria

epidemic, political instability, etc., although the system did not completely collapse.

During the early 19thcentury the colonial government of the time did not allow the people to

restore or repair their sluices or tanks, but later identified the importance of the tank system for

the human livelihood in the dry-zone (Levers 1890). However, the poor knowledge on the

function of the systems had lead to either ignorance or unplanned disruption of the ancient tank

systems during large-scale irrigation development projects during 20thcentury. As the

centralized large-scale schemes were considered to be more efficient than the decentralized small

systems, a number of small tank cascades were replaced by large reservoirs and high capacity

feeder channels.

However the modern development has not been able to capture the harmony between local and

regional hydrological characteristics that the older small cascade tank systems and ancient large

reservoirs could capture so admirably. One of the examples is the function of the giant feeder

canals, which Brohier (1937b) describes in relation to one such canal, as The Jayaganga, indeed

an ingenious memorial of ancient irrigation, which was undoubtedly designed to serve as a

combined irrigation and water supply canal, was not entirely dependent on its feeder reservoir,Kalaweva, for the water it carried. The length of the bund between Kalaweva and Anuradhapura

intercepted all the drainage from the high ground to the east which otherwise would have run to

waste. Thus the Jayaganga adapted itself to a wide field of irrigation by feeding little village

tanks in each subsidiary valley, which lay below its bund. Not infrequently it fed a chain of

village tanks down these valleys the tank lower down receiving the overflow from the tank

higher up on each chain. The photo 6 shows a modern feeder canal that is entirely dependent

on the feeder reservoir as it shuts off the valley drainage by the high embankments. In contrast

the Photo 7 shows the ancient feeder canal, which is now located a few tens of meters below the

modern construction, having one embankment open to catch the runoff and following the

contour lines that result in very low velocity and minimum loss of command area. The

multifaceted functionality of ancient systems has given rise to a renewed interest to scientifically

understand the function of the tank systems in recent times. The ancient irrigation systems have

been developed and constructed over 1600 years, and the collective wisdom of those long years,

in addition to the natural selection process that must have eliminated the unsustainable practices

should be embedded in the remaining systems. It is therefore, very important to rehabilitate and

scientifically understand their functions and services adequately. There have been a number of

large-scale development projects involving reservoirs and diversions providing irrigation to the

dry-zone recently (most rapid developments during 70s and 80s), making it difficult to ascertain

their long-term impact on ecosystems, biodiversity and man-made habitats associated with tanks.

The ancient systems could provide valuable insights to make them sustainable and attractive.

On another aspect, recent research has indicated that the abandoned ancient tanks in the dry-zone

plays a large role as breeding media for malaria vectors (Amerasinghe et al. 2001). It was

recommended that the rehabilitation, use and proper maintenance of village tanks is important to


5/15

the reduction of malaria epidemic in the dry-zone.

The Minneriya Tank, build in 227 A.D. with a circumference of 32 km with a capacity of 136

million cubic meters has been irrigating farms un-interrupted till present. The operation and

maintenance know-how of such reservoirs were lost in the wars in when the families entrusted

with the maintenance of large tanks were killed in 16 thand 17thcenturies. What ever remained

was lost during the colonization and modernization of the last couple of centuries. It is a greatchallenge as well as a national priority to search, un-cover and combine whatever knowledge that

remain with isolated individuals to document this great heritage and to inform the future

generations.

4. Policy and Development Relevance

Sri Lankas per capita rice consumption is about 150 kg/year, out of which only less than 10% is

imported. Hence, a stable rice production remains an important requirement for sustainable

development and alleviation of poverty and hunger in the country. Additionally, each effort insecuring reliable water supplies is extremely important to reduce the widespread poverty in the

rural agricultural areas in the dry zone. Towards this goal, the ancient irrigation works in Sri

Lanka is a crucial component. The government of Sri Lanka launched a project to rehabilitate

1000 village tanks during the year 2004. Now the project is in its 2 ndphase, targeting the

reconstruction of another 1500 tanks at an estimated cost of 70 million Sri Lankan Rupees. The

proper understanding of the function of small tank systems would make it possible to contribute

scientifically for such development attempts.

5. Global Importance

The ancient irrigation systems of Sri Lanka are a unique system that have been perfected through

consistent improvements and construction over 1600 years. The systems consist of many of the

features now we have come to realize as imperative for sustainable utilization. They have

bridged the micro and macro with small village cascades linked up with massive reservoirs in

intricate hydraulic systems. They have succeeded in developing social systems for the

management and operation of the systems where the villagers managed small village tanks and

large reservoirs were managed and operated by designated families. The management systems

encompassed the water management as well as social harmony where collective decisions have

been taken to accommodate high climate variability characteristic of the tropics.

The tank irrigation systems also had the unique feature of blending seamlessly to the naturalenvironment. It is nearly impossible to separate the man-made tank based agricultural

environment from that of the natural environment. This has been carefully maintained through

the preservation of a diverse array of plants and trees that occupied the surrounding land with

paddy. The lessons and experiences from these systems can be very useful in the quest of various

development alternatives, especially for eco-development pursuits.

The sustainable development challenges lie in understanding the human and social needs and

meeting them through the co-existence with nature. In this context, reviving the ancient irrigation

systems in modern day social context by expanding their services to accommodate current

societal needs while designing norms and procedures for community based management of these

systems to be sustainable eco-systems would be a worthy endeavour that identify closesly withthe objectives of GHIAS.


6/15

References:

Amerasinghe, F.P. et al. (2001) Small Irrigation Tanks as a Source of Malaria Mosquito

Vectors: A Study in North-Central Sri Lanka, Report 57. International Irrigation

Management Institute, Colombo, Sri Lanka.

Avsadahamy, U.B. (2003) Wewa, Siri printers, ISBN-955-96820-0-8

FAO (2000)Riceinfo, Crop and Grassland Commission of Internatinal Rice Commision. Food

and Agriculture Organization of the United Nations.

Brohier R. L. (1934), Ancient Irrigation Works of Ceylon Vol 1, 2 and 3, Ceylon

Government Press.

Brohier R. L. (1937a), Inter-Relation of groups of ancient reservoirs and channels in Ceylon.

Journal of Royal Asiatic Society, Ceylon Branch, 34 (90), pp 64-85.

Brohier R. L. (1937b), Interconnected large reservoirs and channels in ancient Rajarata,

Journal of Royal Asiatic Society, Ceylon Branch .

Goldsmith, E. and N. Hildyard (1984), Chap. 24 The Social and Environmental Effects of Large

Dams: Volume 1. Overview. Wadebridge Ecological Center, Worthyvale Manor

Camelford, Cornwall PL32 9TT, UK

Kennady, J.S. (1933), Evolution of scientific development of village irrigation works in Ceylon,

Proc: Engineering association of Ceylon, pp.229-320.

Leach, E. A. (1959), "Hydraulic Society in Ceylon". Past and PresentNo 15.

Levers, R.W. (1890) Irrigation, Chapter 11 of Manual of the North Central Province, pp. 132-

169

Madduma Bandara, C. M. (1994) Tank cascades in Sri Lanka. In. K .Asharul Haq. ed.

Proceedings of IRMU Seminar Series. Colombo: Irrigation Research and Management

Unit/Irrigation Department Sri Lanka

Mendis, D.L.O. (2003), Environment and Conflict: A Kuhnian Paradigm-based approach to

understanding some socio-cultural and economic causes of problems and conflicts in

modern irrigation projects in southern Sri Lanka, in Water for people and nature, Ministry

of Irrigation and Water Management, Sri Lanka, pp.95-122.

Needham, J., Science and civilization in China (1956). Volume IV part 3: Civil Engineering and

nautics.

Panabokke, C. R. 1999. The small tank cascade systems of the Rajarata: Their setting,

distribution patterns, and hydrography. Colombo, Sri Lanka: Mahaweli Authority of Sri

Lanka.

Parker, H. (1909). Ancient Ceylon, London-Luzca & Co., Published by the India Office.

Sakthivadivel, R., Fernando, N. and Brewer, J.D. (1997), Rehabilitation Planning for Small

Tanks in Cascades: A Methodology Based on Rapid Assessment, Report 13: InternationalIrrigation Management Institute, Colombo, Sri Lanka.


7/15

Figures and Maps

Figure 1 Distribution of ancient irrigation systems in the North Central Province


8/15

Figure 2: A cascade system and the micro-watersheds associated withit. (Source: Madduma Bandara1994)


9/15

Figure 3: Interconnected tanlk cascades and large reservoirs on Natural Drainage System in

Anuradhapura District, North-central province, Sri Lanka (Source:


10/15

Figure 4 short sluice perspective (source: Udula Bandara Awsadahamy, 2003)

Figure 5 short sluice cross section (source: Udula Bandara Awsadahamy, 2003)

Figure 6. Bisokotuwa the sluice used in large reservoirs (source: Udula Bandara Awsadahamy,2003)


11/15

Figure 7 Plan view of Bisokotuwa (source: Udula Bandara Awsadahamy, 2003)

Figure 8 Details of Bisokotuwa (source: Udula Bandara Awsadahamy, 2003)

Table 1. Sizes of some reservoir bunds (source: Henry Parker)

-

-

-

-

-

-

-


12/15

Photos

Photo 1 The ancient irrigation tanks not only provided much needed irrigation water to the but

were aesthetically pleasing structures that fit seamlessly with the nature

Photo 2 There are over 30,000 tanks of various sizes built over 1600 years with majority being

constructed from 3 century BC to about 12 century AD


13/15

Photo 3 The length of a an embankment of a tank could vary from few 100 s of meters to 10s of

kilometres .

Photo 4. Sluice gates provided the water to irrigation distribution canals that fed the rice fields.


14/15

Photo 5. The village tank also serves as the community bathing place and plays an important role

as a place for social gatherings.

Photo 6 A recent feeder canal that runs close to the ancient feeder canal. The velocity is muchhigher in the recent construction compared to the ancient one. The high embankments isolate the

canal from the intermediate runoff.


15/15

Photo 7 An ancient feeder canal that lies just below the recent replacement shown in Photo 6.

Note the almost stationary flow, due to construction along the contours. The embankment is only

on the lower side, enabling the canal to trap surface runoff along its way.

srilanka ancient irrigation proposal

Documents